Good question. I have only been on one Celebrity cruise so far, the Summit, and I probably saw less than a dozen kids the entire time. However.... I'm following your logic. On Royal's Vision of the Seas over Easter break, the ship was full of families / kids. Since the Vision doesn't have all the fun, kid friendly activities that the mega ships have, they made their own fun and games. Running up and down the stairs, running through the lounges, playing tag, throwing balls across the centrum. These were mostly young teens, pre-teens. I came to the conclusion that maybe there wasn't enough entertainment on sea days to keep their interest.